Lithium ion secondary battery

Abstract

A lithium ion secondary battery with high reliability and high safety is provided. The lithium ion secondary battery includes a positive electrode for occluding and releasing lithium ions, a negative electrode for occluding and releasing lithium ions, a non-aqueous liquid electrolyte containing a lithium salt, and a separator disposed between the positive electrode and the negative electrode. The positive electrode includes particles of polymethyl methacrylate. Preferably, particles of positive electrode active material in the positive electrode are covered with the particles of polymethyl methacrylate.

1 . A lithium ion secondary battery comprising:
 a positive electrode for occluding and releasing lithium ions;   a negative electrode for occluding and releasing lithium ions;   a separator disposed between the positive electrode and the negative electrode; and   a non-aqueous liquid electrolyte containing a lithium salt;   wherein particles of polymethyl methacrylate exist between particles of positive electrode active material in the positive electrode, the particles of polymethyl methacrylate being in contact with surfaces of the particles of the positive electrode active material.   
     
     
         2 . The lithium ion secondary battery according to  claim 1 ,
 wherein the particles of the positive electrode active material are mixed with the particles of polymethyl methacrylate.   
     
     
         3 . The lithium ion secondary battery according to  claim 1 ,
 wherein each of the particles of the positive electrode active material is directly covered with the particles of polymethyl methacrylate.   
     
     
         4 . The lithium ion secondary battery according to  claim 1 ,
 wherein the positive electrode active material includes 5 weight percent polymethyl methacrylate or less.   
     
     
         5 . A lithium ion secondary battery comprising:
 a positive electrode for occluding and releasing lithium ions;   a negative electrode for occluding and releasing lithium ions;   a separator disposed between the positive electrode and the negative electrode; and   a non-aqueous liquid electrolyte containing a lithium salt;   wherein the positive electrode includes particles of polymethyl methacrylate.